The present invention generally relates to a cab window lock system installed in a cab of a construction machine, and more particularly, to a cab window lock system for locking, at a desired position, a cab window such as a front window which is openable by pulling-up operation.
An openable front window is usually provided for, for instance, a cab of a construction machine, at the front part thereof, for viewing the state of operation being carried out with the front implements. A typical front window is designed to be retractable to its housing position, by pulling it once frontward, pulling it up and backward, and then moving it to the ceiling side of the cab.
Generally, this front window should be fixedly installed on the front side of the cab such that rain and dust cannot penetrate into the cab from outside when it is in service, and should be stably held at its housing position when it is opened. To this end, such a front window is conventionally provided with a lock mechanism of the bolt (lock pin) type such as disclosed in Japanese Patent Publication (KOKAI) Gazette No. 10-311061 (1998). This mechanism has lock pins which are disposed on both ends of the top portion of a window frame so as to be fittable in engagement holes defined on the front pillars of the cab etc. At the time of opening or closing the window, the window is unlocked or locked, by pulling out or inserting the lock pins of the lock system relative to the holes. This prior art lock mechanism includes a holding mechanism in which holding levers are automatically brought into engagement with a roller shaft of the window frame upon arrival of the window frame at its travel end when it is moved to its housing position so that the window frame is held so as not to move back from the housing position.
In place of the above lock-pin type lock mechanism, another lock mechanism is proposed in Japanese Patent Publication (KOKAI) Gazette No. 10-311062 (1998) according to which latches are provided so as to rotate into engagement with strikers fixedly mounted on a structure (the body of a cab). In this lock mechanism, strikers in the form of  (Japanese katakana letter xe2x80x9ckoxe2x80x9d) are secured to the body of a cab, while two plate members each having an engagement groove are attached through brackets to a movable window frame at its upper and lower positions so as to work and turn in cooperation. When these plate members are released from a fastened condition by one release lever, the opposed engagement grooves of the plate members are respectively opened to the strikers by virtue of the force of torsion springs, receiving the strikers in a biting manner so that the engagement grooves are brought into locking engagement with the strikers. For unlocking the window, the plate members are respectively turned by the release lever in the direction opposite to the turning direction adapted at the time of engagement so that disengagement is established.
Japanese Patent Publication (KOKAI) Gazette No. 8-312220 discloses a lock mechanism having one latch capable of engaging with a moveable member provided at a home position and another moveable member provided at a position to which a door is moved. This mechanism uses, in combination, lock grooves (notches) formed on a turnable lock plate so as to be oriented in two different directions and a lock releasing lever for restricting the turn of the lock plate. When opening or closing the sliding door, a handle is operated to release the lock plate from the restriction by the lock releasing lever, so that the lock grooves of the lock plate are disengaged from lock pieces as the door moves. Then, upon arrival of the door at its sliding end, the lock grooves come in contact with lock pieces provided at this position so that the door is locked.
However, the lock-pin type lock mechanism of Japanese Patent Publication No. 10-311061 has a problem in its operablility that the lock pins have to be positioned relative to the lock holes for insertion and have to be anchored in the lock holes by rotation in order to prevent them from coming off. In addition, it is necessary to provide a radial gap between each pin and each pin hole (i.e., lock hole) in order to facilitate the positioning of the lock pin relative to the pin hole for insertion. The front window chatters with vibration all the more for the gap, generating noise and causing wear of the pin hole which brings about further vibration.
Another disadvantage of the system of this publication is that it needs a lock mechanism for locking the front window at the fixed position and a holding mechanism for holding it at the housing position, these mechanisms being different in structure. This is because the direction of locking the front window is utterly different from the direction of holding it. Therefore, the locking operation and the unlocking operation differ from each other, which leads to poor operability.
The lock mechanism having a latch and disclosed in Japanese Patent Publication No. 10-311062 involves a complex structure in which two plate members which respectively have an engagement groove are vertically arranged in an opposed relationship and these plate members cooperate to open and close their engagement grooves. In addition, this lock mechanism effectively functions in locking a window in an upright condition but cannot provide good stability when it is applied to the window in other conditions.
The lock mechanism disclosed in Japanese Patent Publication No. 8-312220 is advantageous in that two-directional operation can be performed, but the arrangement disclosed in this publication is insufficient to lock or hold the window frame at its travel end by use of only one latch (lock plate), the window frame being movable while changing its posture from an upright condition to a horizontally lying condition. More concretely, two different functions are required in locking and holding the window frame which moves upward changing its posture from an upright condition to a horizontally lying condition, one being a function for locking the window so as to press the window frame against a support structure at the periphery of the window when the window frame is in its upright position, while the other being a function for supporting the window frame which is coming down because of gravity and holding it so as not to move back when the window frame is in its upper, housing position. There is a difficulty in adapting the latch mechanism disclosed in the above publication to a cab window which requires the above functions.
The present invention is directed to overcoming the foregoing problems. Therefore, a first object of the invention is to provide a cab window lock system which is simple in structure and enables stable, easy locking operation and unlocking operation.
A second object of the invention is to provide a cab window lock system capable of reliably closing and fixing a window of the lift open type at its closing position, and reliably holding and housing it at its upper housing position.
The first object of the invention can be achieved by a cab window lock system according to a first aspect of the invention.
This lock system is composed of lock mechanisms each comprising a turnable latch and a release lever for restricting the turn of the latch in its disengaging direction,
each of the lock mechanisms further comprising a release lever disengagement maintaining mechanism which comes into engagement with the release lever to keep the release lever in its disengaging condition at a disengaging position where the latch is disengaged from the release lever,
the release lever disengagement maintaining mechanism being designed to release the release lever from its disengaging condition when the latch has turned through a specified rotation angle.
According to the invention arranged as described above, if the release lever is operated to cancel the engagement between the latch and the release lever thereby unlocking the latch, the release lever disengagement maintaining mechanism is operated, in conjunction with the latch unlocking operation by the release lever, to temporarily hold the release lever to prevent it from returning. Thus, the latch becomes free and is turned by an extrinsic turning force so that the latch can be unlocked. The turn of the latch in its disengaging direction causes a shift of the position of engagement between the latch and the release lever, and accordingly, the latch works on the release lever disengagement maintaining mechanism such that the release lever is released from its disengaged condition. Then, when the latch comes into engagement with a striker (closing bolt), exerting its locking function, the release lever returns to a position where it can engage with the latch.
Since the lock system of the invention is designed as described above, when the latch is unlocked by manipulating the latch release lever in releasing operation, the latch automatically becomes free, and therefore there is no need to hold nor handle the release lever afterward. This arrangement contributes to improved operability, particularly where a plurality of lock mechanisms need to be unlocked.
In the invention, the release lever disengagement maintaining mechanism comprises: a release lever latch which is supported on a support shaft of the latch and which is turnable together with the latch only when the latch turns in its disengaging direction; a striker which is disposed adjacently to an engagement end of the release lever for holding the release lever; and a spring for energizing the release lever latch such that the release lever latch turns in a returning direction. With this arrangement, the mechanism for maintaining the release lever in its disengaged condition can be disposed coaxially with the latch, which makes the whole system compact and reduces the number of parts, resulting in a saving of cost.
In this case, the release lever latch preferably includes an engagement recess which comes into engagement with the striker for bringing the release lever to a stop and a projection which extends continuously from the engagement recess. The distal end of the projection is preferably arranged such that the striker is positioned within the radius of gyration of the distal end of the projection when the latch is kept in its engaged condition by the release lever, and such that the striker reaches a position beyond the radius of gyration of the distal end of the projection when the release lever is shifted until the latch""s engaged condition by the release lever is cancelled. With this arrangement, at an instant when latch disengaging operation is performed by the release lever, the striker attached to the distal end of the release lever comes in contact with the distal end of the projection of the release lever latch so that the release lever is prevented from returning, whereby the release lever can be reliably maintained in its disengaged condition. Additionally, the turn of the latch after the disengagement permits the striker formed on the release lever to be restorable and when the latch is engaged the next time, the release lever can be stably maintained in its engaged condition with the striker being positioned within the radius of gyration of the distal end of the projection.
The release lever disengagement maintaining mechanism may comprise a lock claw piece having a base pivotally supported in the neighborhood of the engagement end of the release lever and a distal end facing the distal end of the release lever; an operating pin attached to the lock claw piece for operating the lock claw piece by the turn of the latch; and a spring for energizing the lock claw piece so as to invariably move in the direction of the axis of rotation of the latch, and the striker may be operated by the lock claw piece. The striker may be located within the radius of gyration of the distal end of the lock claw piece when the latch is in its engaged condition and the striker may reach a position beyond the radius of gyration of the distal end of the lock craw piece when the release lever is shifted until the latch""s engaged condition is cancelled.
With this arrangement, when unlocking the window by operating the release lever so as to be disengaged from the latch, the projection formed on the outer side face of the latch-engagement end of the release lever is brought into contact with the distal end of the lock claw piece to push the lock claw piece outward. Then, the lock claw piece pivots on the pivotal point on the base, so that the lock claw piece is disconnected from the projection on the latch engagement end of the release lever and the projection is anchored after moving to a position beyond the distal end of the lock claw piece. As a result, the latch can freely rotate in a disengaging direction by virtue of a rotation force caused by an energized, torsion spring or the like and is disengaged from the striker, thereby unlocking the structure (such as a door and window) to which the lock system is attached. When the latch turns, the peripheral face of the latch pushes the operating piece outward, thereby moving the lock claw piece outward to make the release lever free, so that the release lever returns to the latch side. Therefore, when the latch is engaged with the striker in the next time, the engaging part of the latch can engage with the engagement end to enable locking. In this way, the release lever disengagement maintaining mechanism can surely release the release lever in conjunction with a latch disengaging operation without difficulties. After being released, the release lever can be automatically restored in conjunction with the disengagement of the latch so that it is ready for the next locking operation.
The second object can be accomplished by a cab window lock system constructed according to a second aspect of the invention.
This lock system is designed to accommodate a window frame in its housing position such that the window frame is oriented in a direction transverse to the direction in which the window frame is oriented when it is in its upright-standing home position, by moving the window frame upward from the upright-standing home position, the window frame being movable along a pair of guide rails attached to a support structure. This lock system is constructed such that lock mechanisms are respectively attached to both ends of a top part of the window frame, so as to be exterior to the window frame and interior to the guide rails in the direction of width, each of the lock mechanisms having a latch including two engagement notches at positions which are a specified angle displaced from each other and a release lever for restricting the turn of the latch and disengaging the latch, and such that strikers are respectively disposed at the upper part of the upright-standing home position for the window frame and at the terminal end of the housing position for the window frame, for engaging with the engagement notches of the latches to hold the window frame, the strikers being attached to the support structure so as to be parallel with the axis of rotation of the latches.
In the invention thus designed, each of the lock mechanisms disposed at both ends of the top part of the window frame includes a turnable latch provided with two engagement notches having different engaging directions. At the window locking position in which the window is closed and at the housing position in which the window frame is housed after moving upward sequentially to opening of the window, the window frame can be fixedly positioned, by changing the engaging direction of the latch according to a change in the posture of the window frame by means of the strikers attached to the support structure and the engagement notches formed in the latch. With this arrangement, the window frame can be securely, reliably fixed and held by only one latch even though the window frame assumes different postures. In addition, since the lock system can be made in a simple structure provided with one turnable latch and a release lever for restricting the turn of the latch (i.e., locking) and disengaging the latch (i.e., unlocking), installation space can be saved and the window frame can be easily pulled up from its upright standing condition in order to house it.
In the invention, preferably, each of the latches has an engagement notch which comes into engagement with a first striker at a position above a rotating support shaft in order to lock the window when the window is closed, the first striker being fixedly supported by the support structure so as to project therefrom; and has an engagement notch which comes into engagement with a second striker at a position below the rotating support shaft in order to hold the window frame when the window frame is at the window-opening, housing position, the second striker being fixedly supported in the window-opening, housing position by the support structure so as to project therefrom.
With this arrangement, when moving the window frame at the window closing position so as to be pushed forward for closing the window, one of the engagement notches is brought into engagement with the first striker disposed in the above position, whereby the latch and the release lever can be connected in the neighborhood of the window frame, resulting in a compact structure. In addition, the two engagement notches formed in the latch radially open, and the position of the first striker located in the window closing position is upper than the position of the rotating support shaft of the latch, whereas the position of the second striker located in the housing position is lower than the position of the rotating support shaft of the latch. With this arrangement, when moving the window frame toward the housing position after pulling it up and opening the window, the other engagement notch of the latch can be brought into engagement with the second striker provided in the housing position without any special operation so that lock can be established. In this way, the window can be automatically locked only by pulling up and moving the window frame toward the housing position, which leads to improved operability.
It is also preferable that a striker trapping end of the opening of each engagement notch formed in each latch is longer than a striker holding end thereof. This enables it to stably maintain the engagement/holding of the strikers when the window is locked.